The freeze-free season is defined as the period of time between the last spring frost (daily minimum temperature below 32 degrees F) and the first fall frost. The length of the annual freeze-free season has been increasing since the 1980s, and all climate models agree that it will continue to increase in the future. The largest increases are projected for the areas west of the Cascades, with some areas increasing by more than 40 days. The rest of the region is expected to have roughly 25-day increases in the growing season.